1. Field of the Invention
The instant disclosure relates to a light emitting diode (LED) package; in particular, to a composite LED package including the processing of LED lamp package and surface mounted device (SMD) package. The composite LED package allows for a wider viewing angle and applies to light tubes.
2. Description of Related Art
Due to the fast improvement of light emitting diode (LED) technology, LED has been widely used in lighting. LED lamp package, surface mounted device (SMD), flip-chip and chip on board (COB) are common methods for producing LED. However, after packaging, the viewing angle of LED is relatively restricted by the packaging materials and configuration. The resulting viewing angle is less than 180° let alone a desired 360° viewing angle. The LED package for lighting has been changed because of the enhancement of LED chip performance and packaging. From LED lamp package, SMD, PLCC, High-Power, Multi-Chips to the most widely used COB, the viewing angle is fixed. For example, as shown in FIG. 1A, a conventional LED lamp package 100′ includes an LED die 1′ and a pair of pins 2′. One of the pins 2′ is configured to a reflector cup 3′ for retaining the LED die 1′. A plastic lens 4′ encloses the LED chip 1′ and the reflector cup 3′. The reflection cup 3′ confines the LED light emitting direction.
Additionally, as shown in FIG. 1B, a conventional SMD package 200′ includes a substrate 10′ formed by injection molding. A lead frame 11′ is fastened on the substrate 10′ and together they form a packaging substrate. An LED die 12′ is attached onto the lead frame 11′ and an optical lens 14′ covers the top of the substrate 10′. One electrode of the LED die 12′ is immediately electrically connected to the lead frame while the other electrode is connected by wire bonding to the lead frame by a bond wire 15′. The non-translucent and heat resistant substrate 10′ also confines the LED light emitting direction. When the LED chips illuminate, a portion of light is absorbed by the substrate 10′, or light reflection and refraction occur. Most of the light is absorbed after several rounds of reflection and refraction. Therefore, the luminance of the LED device is greatly compromised and energy is wasted in the internal light propagation. Furthermore, the conventional SMD package requires higher fabrication cost because the manufacturing process includes metal pressing and plastic injection molding to form the costly heat resistant substrate 10′.
Moreover, the conventional lens is made of highly translucent resin or other plastic materials and the light rays are concentrated on/at a bright spot. The viewing angle rarely exceeds 90° and mostly falls between 18° and 60°. Even the most widely used COB LED only provides a viewing angle less than 180°. A 360° viewing angle is desired in various applications. The incandescent lamp and fluorescent lamp have a wider viewing angle and are cost effective, thus more appealable to the consumers than the LED.